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  2. Flatness problem - Wikipedia

    en.wikipedia.org/wiki/Flatness_problem

    The relative density Ω against cosmic time t (neither axis to scale). Each curve represents a possible universe: note that Ω diverges rapidly from 1. The blue curve is a universe similar to our own, which at the present time (right of the graph) has a small | Ω − 1 | and therefore must have begun with Ω very close to 1 indeed.

  3. Black hole cosmology - Wikipedia

    en.wikipedia.org/wiki/Black_hole_cosmology

    A black hole cosmology (also called Schwarzschild cosmology or black hole cosmological model) is a cosmological model in which the observable universe is the interior of a black hole. Such models were originally proposed by theoretical physicist Raj Kumar Pathria , [ 1 ] and concurrently by mathematician I. J. Good .

  4. Cosmological horizon - Wikipedia

    en.wikipedia.org/wiki/Cosmological_horizon

    It represents the boundary between the observable and the unobservable regions of the universe, so its distance at the present epoch defines the size of the observable universe. Due to the expansion of the universe, it is not simply the age of the universe times the speed of light, as in the Hubble horizon, but rather the speed of light ...

  5. Observable universe - Wikipedia

    en.wikipedia.org/wiki/Observable_universe

    Observable Universe as a function of time and distance, in context of the expanding Universe The universe's size is unknown, and it may be infinite in extent. [ 14 ] Some parts of the universe are too far away for the light emitted since the Big Bang to have had enough time to reach Earth or space-based instruments, and therefore lie outside ...

  6. Horizon problem - Wikipedia

    en.wikipedia.org/wiki/Horizon_problem

    Conformal time describes the amount of time it would take a photon to travel from the location of the observer to the farthest observable distance (if the universe stopped expanding right now). The blue circle is the CMB surface which we observe at the time of last scattering.

  7. Lambda-CDM model - Wikipedia

    en.wikipedia.org/wiki/Lambda-CDM_model

    The actual observable amount of lithium in the universe is less than the calculated amount from the ΛCDM model by a factor of 3–4. [ 83 ] [ 2 ] : 141 If every calculation is correct, then solutions beyond the existing ΛCDM model might be needed.

  8. Event horizon - Wikipedia

    en.wikipedia.org/wiki/Event_horizon

    The reachable Universe as a function of time and distance, in context of the expanding Universe. In cosmology , the event horizon of the observable universe is the largest comoving distance from which light emitted now can ever reach the observer in the future.

  9. Cosmography - Wikipedia

    en.wikipedia.org/wiki/Cosmography

    In astrophysics, the term "cosmography" is beginning to be used to describe attempts to determine the large-scale matter distribution and kinematics of the observable universe, dependent on the Friedmann–Lemaître–Robertson–Walker metric but independent of the temporal dependence of the scale factor on the matter/energy composition of the Universe.